1. Field of the Invention
The present invention relates to lining techniques, and more particularly to a method of lining inner walls of aged or defective branch pipes.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. Typically, the method is disclosed by Japanese Provisional Patent Publication (Kokai) No. 60-242038.
According to the method described in the above-mentioned publication, the pipe repair method comprises inserting a sufficiently long tubular flexible liner bag into the pipe to be repaired by means of a pressurized fluid, like air and water. The tubular liner bag is made of a flexible resin-absorbent material impregnated with a thermosetting resin, and has the outer surface covered with an impermeable plastic film.
More particularly, according to the publication, the tubular flexible liner bag is closed at one end and open at the other; the tubular flexible liner bag is first flattened, then, the closed end of the tubular liner bag is tied to a control rope; the open end of the tubular liner bag is made to gape wide and hooked (anchored) at the end of the defective or old pipe in a manner such that the wide-opened end of the liner completely and fixedly covers and closes the pipe end; a portion of the liner is pushed into the pipe; then, the pressurized fluid is applied to the portion of the tubular liner such that the fluid presses the tubular liner to enter the pipe. Since one end of the tubular liner is hooked at the end of the pipe, it remains there while the rest of the flexible liner bag is turned inside out as it proceeds deeper in the pipe. (Hereinafter, this manner of procedure shall be called "everting".) When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the control rope holds the closed end of the tubular liner bag to thereby control the length of the tubular liner in the pipe. Then, the everted tubular liner is pressed against the inner wall of the pipe by the pressurized fluid, and the tubular flexible liner is hardened as the thermosetting resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular lines bag by means of a hot steam, etc. It is thus possible to line the inside wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
The above-mentioned method may also be applied to the lining of a branch pipe which is branched from a main pipe, an example of which is illustrated in FIG. 10.
FIG. 10 is a cross-sectional view showing a conventional method of lining a branch pipe. A pressure bag 112 for everting a branch pipe liner bag 104 is inserted into a main pipe 101. A branch pipe 102 to be repaired is branched from the main pipe 101 as illustrated. Since this pressure bag 112 must be separated from the branch pipe liner bag 104, a sealing tube 140 should be connected to the pressure bag 112 in order to apply a pressure to the branch pipe liner bag 104.
Then, the pressure bag 112 is supplied with compressed air to evert both the sealing tube 140 and the branch pipe liner bag 104 into the branch pipe 102. While the illustrated state is being maintained, the branch pipe liner bag 104 is, for example, heated to harden a hardenable resin impregnated therein. Thereafter, when the sealing tube 140 is pulled out from the branch pipe 102 (branch pipe liner bag 104), the branch pipe 102 is reinforced by the hardened branch pipe liner bag 104 which has been lined on the inner wall of the branch pipe 102.
The above-mentioned method, however, must prepare the sealing tube 140 of an appropriate length in accordance with variations in length of the branch pipe 102 each time it is to be repaired. Therefore, the sealing tube 140 must be exchanged for each branch pipe according to its length.
To solve this problem, a branch pipe lining method as shown in FIGS. 11 and 12 has been proposed.
More specifically, FIGS. 11 and 12 are cross-sectional views used for explaining a conventional branch pipe lining method which does not need a sealing tube as that indicated by 140 in FIG. 10. This method utilizes a separator tube 240 to realize an air-tight connection between a pressure bag 212 for eversion and a branch pipe liner bag 204. One end of the separator tube 240 is temporarily connected to the branch pipe liner bag 204. In FIG. 11, reference numeral 241 designates a guide tube; 242 an air mat for pressing a flange 204a of the branch pipe liner bag 204 against the inner wall of a main pipe 201; and 203 a robot introduced into the main pipe 201 for the lining operations.
With the flange 204a of the branch pipe liner bag 204 being pressed against the inner wall of the main pipe 201, as shown in FIG. 11, compressed air supplied to the pressure bag 212 causes the branch pipe liner bag 204 to be everted by the pressure of the compressed air and inserted into the branch pipe 202 in the direction indicated by a white arrow. When the insertion of the branch pipe liner bag 204 has been completed, a hardenable resin impregnated in the branch pipe liner bag 204 is hardened, whereby the inner wall of the branch pipe 202 is lined or repaired by the hardened branch pipe liner bag 204.
Referring now to FIG. 12, when the branch pipe 202 has been lined, the pressure bag 212 is moved in the direction indicated by arrows. Since the pressure bag 212 is coupled with the robot 203 through the guide tube 241, the robot 203 is also moved in the same direction. Further, the separator tube 240 temporarily connected to the branch pipe liner bag 204 is torn off from the temporarily connected area so that it is separated from the branch pipe liner bag 204.
As described above, since this conventional method utilizes the separator tube 240 to realize an air-tight connection between the pressure bag 212 and the branch pipe liner bag 204, the same separator tube 240 can be used irrespective of the length of a branch pipe to be repaired, so that the exchange of the sealing tube 140, which would be required by the method shown in FIG. 10, is made unnecessary.
The proposed method however has a drawback that the separator tube 240 may not be completely torn off so that part thereof remains on the inner wall of the branch pipe liner bag, wherein the remaining part acts as burr to cause an unfavorable condition of the inner wall. Specifically, flowing substances within the branch pipe may attach to the burr.